The most common mode of polymerization of commercial grades of polystyrene utilizes free radicals, and is thus called “free radical polymerisation”. Anionic polymerisation has tremendous polymerisation rate advantages over free radical. In spite of this rate advantage, however, anionic polymerisation has been utilized commercially only in limited areas, generally not involving polystyrene. Most of the useful areas have involved copolymerisation to produce block copolymer type elastomers. The rapid rate of anionic polymerization has actually inhibited the commercial development for polystyrene, due to difficulty in removing heat fast enough to control the highly exothermic reaction. Several companies have explored and patented techniques for dealing with this rapid rate of polymerization.
Another very serious, but less discussed, problem is “gel” formation. Technology of dealing with both the rapid rate of polymerisation and gel formation is key to commercialisation of anionic polystyrene and both are contained in this patent.